[LLVMdev] Multi-Instruction Patterns
evan.cheng at apple.com
Wed Sep 24 13:34:19 CDT 2008
On Sep 24, 2008, at 10:16 AM, Chris Lattner wrote:
> On Sep 24, 2008, at 8:44 AM, Dan Gohman wrote:
>>> #2 is conceptually correct. The problem is 128 bit XMM0 is the same
>>> register as 32 bit (or 64 bit) XMM0. So it's not possible to define
>>> the super-register / sub-register relationship.
>> I don't understand the problem with subregs here. Is it just a
>> naming issue? That can be solved by introducing alternate names,
>> like XMM0_32 and XMM0_64, for each of the subregs. They could
>> still be printed as "xmm0" in the assembly output of course.
> this is what the PPC64 backend does. "X0" (64-bit GPR) and "R0" (32-
> bit GPR) both print as "r0".
Somewhat different scenario there. On PPC64, these are actually
distinct registers, right?
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